Field of the Invention
The invention relates to a configuration for the inscription of wafers. The inscription includes a coding and is applied by using a laser.
Semiconductor wafers are provided with a wafer identification on the front before manufacture. The wafer identification or marking is fused in by laser and is used to distinguish between the wafers and to distinguish between entire manufacturing batches. Furthermore, information is included about the assignment of manufacturing and product data. Thus, with its marking, each wafer bears the essential information for its identification and for defining the processing on the wafer. That results in the requirement that the wafer marking must be legible until the final manufacturing step.
As a result of the increasing number of processes and the use of so-called CMP (chemical mechanical polishing) processes on the front of the wafer, the marking which is applied to the front is increasingly worn out by the application and removal of coatings. In the end, that leads to the applied marking being erased completely. That problem occurs only with the increased use of CMP processes. Permanent identification of the wafers within process lines can be maintained by using reinscription methods at a suitable point.
The reinscription must be carried out automatically in order to prevent any incorrect, multiple or double wafer marking being applied during the reinscription process.
The use of so-called hardmarks is linked to spattering during the introduction of the marking. That is based on the fact that high-energy laser radiation does not just melt the wafer material but, to some extent, vaporizes it. That leads to yield losses. However, the use of so-called softmarks as an alternative to the deeper hardmarks leads to a marking which is applied on a wafer becoming illegible during the processing involved with the production of semiconductor components.
Previous configurations for wafer inscription include an inscription chamber which is coupled to a laser unit. The only item provided within the inscription chamber is a positioning unit for holding and for exact alignment of a wafer. An inscription check, which is carried out after the inscription process using a read system, takes place outside the inscription chamber, and outside the region in which the positioning unit acts. At least in the case of reinscription processes, that leads to a severe reduction in throughput and, depending on the sequence of the inscription process, to poorer positioning of the reinscription.